The present invention relates to brushes, especially cleaning brushes employed in xerographic printing machines, and more particularly to a cleaner brush for removal of semi-conductive contaminants such as laterally conductive films on a photoreceptor.
In known electrostatographic reproducing apparatii, a photoconductive insulating member is typically charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member which corresponds to the image contained within the original document. Alternatively, a light beam may be modulated and used to selectively discharge portions of the charged photoconductive surface to record the desired information thereon. Typically, such a system employs a laser beam.
Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with developer powder referred to in the art as toner. Most development systems employ developer which comprises both charged carrier particles and charged toner particles which triboelectrically adhere to the carrier particles. During development, the toner particles are attracted from the carrier particles by the charged pattern of the image areas of the photoconductive insulating area to form a powder image on the photoconductive area. This toner image may be subsequently transferred to a support surface such as copy paper to which it may be permanently affixed by heating or by the application of pressure. Usually, all of the developed toner does not transfer to the copy paper, and therefore cleaning of the photoreceptor surface is required prior to the point where the photoreceptor enters the next charge and expose cycle.
Commercial embodiments of the above general processor have taken various forms and in particular various techniques for cleaning the photoreceptor have been used such as a rotary cleaning brush. Generally the bristles of such a cleaner brush are soft so that as the brush is rotated in contact with the photoconductive surface to be cleaned, the fibers continually wipe across the photoconductive surface to produce the desired cleaning without significant wear or abrasion to the photoreceptor.
A problem associated with cleaner brush is the removal of laterally conductive salt deposits on the photoreceptor. The problem is more acute in printing machines employing the image on image (IOI) process in which a relatively gentle non-interactive development system and a brush cleaner system is used. The result is that over time the belt surface becomes increasingly contaminated, leading to image degradation and visualization of interdocument zone features in jobs with mixed media sizes. Applicants have found that Lateral Charge Migration (LCM) manifests itself when abrasion or wear of the photoreceptor is insufficient to remove semi-conductive species that accumulate at the photoreceptor surface as a result of photoreceptor interactions with corona emissions and/or volatile organic contaminants.
Subsequent developments in cleaning techniques and apparatii, in addition to relying on the physical contacting of the surface to be cleaned to remove the toner particles, also rely on establishing electrostatic fields by electrically biasing one or more members of the cleaning system to establish a field between a conductive brush and the insulative imaging surface so that the toner on the imaging surface is attracted to the brush by electrostatic forces. Thus, if the toner on the photoreceptor is positively charged then the bias on the brush would be negative. Therefore, the creation of a sufficient electrostatic field between the brush and imaging surface to achieve the desired cleaning effect is accomplished by applying a DC voltage to the brush.
There has been provided a cleaning system comprising: a cleaning device for cleaning debris from the imaging surface; an AC bias member, adjacent to the imaging surface and positioned upstream from said cleaning device; and a power supply for biasing said AC bias member to generate corona that contacts the imaging surface to degrade LCM contaminates on the imaging surface.
There has also been provided an electrostatic printing machine having a cleaning system comprising: a cleaning device for cleaning debris from an imaging surface; an AC bias member, adjacent to the imaging surface and positioned upstream from said cleaning device; and a power supply for biasing said AC bias member to generate corona that contacts the imaging surface to degrade LCM contaminates on the imaging surface.